Ozzie st150 exhaust

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Re: Ozzie st150 exhaust

Postby Stu » Tue Apr 05, 2016 9:01 am

thanks for the kind words guys :smt023 - so first thing is being in Oz you are at the coast correct ? what other mods do you have on your car ? and what is your goal power wise? reason I ask is that in SA we normally just decat but due to regulations in Oz you have to run a sports cat you also have better fuel quality so depending on what your current mods and what mods you planning on ,will determine what kind of setup will favour you
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Re: Ozzie st150 exhaust

Postby rositano » Tue Apr 05, 2016 11:05 am

Mr Wayne wrote:quote]

Exactly!! Nothing like living on the edge!

Mr Wayne, do you much about st150 back boxes? Noticed a lot of guys in SA have the milltek exhausts with a free flowing back box, but I recall Stu saying that it isn't a straight-through as such. I'm keen to buy a local brand of back box which is similar in design to the milltek, but without the price tag (shipping is a [email protected]!)

Thanks


I drive a 225 bud so I'm not to clued up on the 150, i will say that Stu has one of/if not the fastest 150 on SA roads at the moment so he is pretty much on point when it comes to the fiST![/quote]

No worries, thanks for the heads-up.
I guess I'll just hope that Stu happens to stumble upon this topic then!!

Thanks again

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Re: Ozzie st150 exhaust

Postby rositano » Tue Apr 05, 2016 11:20 am

Stu!! the man himself!! I hear that you're the st150 guru....and rightfully so, after all the time and effort that you've spent on the your st150.
Thanks for the reply.

So...currrent mods:

- enclosed simota sri with cold air feed.
- poly rear engine mount
- lowered on H&R springs
- swr 4-2-1 headers
- 57mm OD 200 cell sports cat
- 60mm OD straight through resonator
- Bluefin stage 2

After the resonator, the remaining exhaust is stock.....and yes, I'm at the coast.

My aim: To modify exhaust (if required) for optimum backpressure and ultimately, best low-end torque. The car is my daily driver, so high-end hp isn't a priority. In the future, I'd be contemplating a set of mild cams and possibly dreamscience software.

Thanks again.

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Re: Ozzie st150 exhaust

Postby Stu » Tue Apr 05, 2016 11:37 am

well from the tests I've done the biggest gains in power come from cams and under drive pulley, adding the 60mm throttle at the coast on stock st150 only gave around 3-5kw more but on a st190+ kit its fantastic add on. when it comes to the exhaust its a bit tricky what I found worked for most of the guys at the coast was to run a 4-2-1 branch like SWR then into a 57mm setup(decat) put the first resonator box around 10cm from the bend by the wheel well, you can then run either 57mm or 60mm to your second and third box if desired(some use 2 boxes some use 3 boxes) - This is the setup for at the coast which seemed to work well especially once you add cams.... up on the reef above sea level(we lose 17% power with normally aspirated cars) we tend to use slightly smaller pipes so 54mm into 57mm setup but the same layout with the first resonator box

also when choosing your cam - remember most cams will take power away from lower in the rpm range and give higher gains up higher in the rpm range.... a good balance I found was the cosworth 200bhp cams as they near same duration as the sock cam but with slightly more lift was great as a daily cam and once you add the under drive kit your power really goes up.. also got better throttle response and much better fuel consumption once the under drive kit was fitted, as its much lighter than the stock ones
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Re: Ozzie st150 exhaust

Postby rositano » Tue Apr 05, 2016 12:08 pm

Excellent info Stu!! Thanks

I attached a sketch of my exhaust in my first post. I added the first resonator directly behind the sports cat. I guess the only variable/unknown element which differs from most of the coastal setups you mentioned is that I have a sports cat as opposed to a decat. I already have this restriction compared to most in SA. This no doubt changes the dynamics of the exhaust.

Would be it OK then to keep my current setup up until my first resonator (directly behind cat), and then change to 57mm pipe all the way to the second resonator (parallel to the rear wheel) and then to the rear muffler?

Thanks

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Re: Ozzie st150 exhaust

Postby Stu » Tue Apr 05, 2016 12:17 pm

ye I would give that a try as it will be the cheapest option and see how it feels :smt023
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Re: Ozzie st150 exhaust

Postby rositano » Tue Apr 05, 2016 12:34 pm

Will do.

Another thing I was curious about Stu, if you don't mind, is about the back box. I know you've commented on this many times before, I was curious about the internal design of the milltek back box. I'm keen to buy a less restrictive one than the stock and have heard good things about the milltek, but to buy and ship one here to Oz is pricey! My plan was to buy a local high quality back box to mimic the milltek internals. Not sure if its a straight through, turbo(reverse flow) or chambered?

Thanks heaps.

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Re: Ozzie st150 exhaust

Postby Stu » Tue Apr 05, 2016 12:36 pm

from when I saw the milltek back box, it isn't a freeflow it looks similar to the inside of a Cat lots of path ways and compartments
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Re: Ozzie st150 exhaust

Postby rositano » Tue Apr 05, 2016 12:46 pm

Interesting!! Some useful info. Online searches haven't revealed much by way of images.

I guess it's trial and error!......you'd know all about that. lol

Thanks again Stu

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Re: Ozzie st150 exhaust

Postby Stu » Tue Apr 05, 2016 12:50 pm

haha yip that's the way trial and error :lol: it just gets costly
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Re: Ozzie st150 exhaust

Postby mohamedeb » Tue Apr 05, 2016 4:53 pm

There's also a screw on the stock throttle that allows you to adjust idle and how responsive the ST150 is. The crank angle sensor found underneath the car has polarity and can be adjusted for responsiveness, idle and can give a little improvement. I know this because my dad and i replaced my st150 with a new engine and my father worked on the loom and sensors himself. Trust me i raced quite a few st150's with branch and exhaust and a good map. You can fine tune it further by hand. Exhaust wise a simple 42 mm 4-2-1 branch. If you live at the coast these cars perform best at very high engine temps. The ceramic coating isn't that important or valuable unless you track the car every weekend. Exhaust, your 57mm 2 box setup with either a slightly bigger backbox or same sized back box should give you ample gains. These mods are safest and work well with no issues. If your st150 takes oil as forum members suggest, then something can't be right. These cars should only take any oil when you give it the beans!

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Re: Ozzie st150 exhaust

Postby rositano » Wed Apr 06, 2016 2:52 am

Hi Mohamed,

That's some interesting info. I remember adjusting the idle screw on the throttle of my other ride prior to buying the st150. It involved a lot of fiddling, trying to get the balance right. Not that experienced with the fezz at the moment, but will most certainly look into it later on. With regards to my exhaust, if you have a look a my sketch in my first post, after my swr branch, sports cat and 57mm resonator, the rest of the exhaust is stock. My plan is to do what many coastal guys on the forum have already done, and that's go 57mm all the way to the back with a less restrictive back box. I just want to ensure that the back box isn't too loud or 'droney'.

Thanks

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Re: Ozzie st150 exhaust

Postby mohamedeb » Thu Apr 07, 2016 3:09 am

Ah dude i wish i cud help u i did my exhaust in march 2014. My back box is pretty big and does differ from the hopeless stock squarish box. My back box has the famous doug wallace like finish. Similar to those roundy back boxes u see on those GT subarus in Aus. If ever my cars on a ramp il snap a pic.

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Re: Ozzie st150 exhaust

Postby mohamedeb » Thu Apr 07, 2016 3:17 am

Well from your sketch i suggest you keep going with a slightly bigger back. Not 54mm though as you may want to put cams and besides a nicely designed backbox surely sounds good. Your resonator design looks good but i once saw an ovalish design that was massive(i think my car). It sounded soo good the guy gave me a choice of 2 resonators. Luckily back then a buddy of mine who used 2 build drag cars designed mine for me by telling the guy how to build my exhaust. Ultimately your power figures will be soo similar to ours as you guys even use the same measurements. Don't break your head. Simply choose what looks good and has classy welds on it. A quality exhaust is better den a crappy loud exhaust. Look at the type of steel or be fancy opt for titanium back boxes which csn be ordered and those can be studded i think. Titanium is stubborn 2 weld. Should sound more raspy i think. Be different!

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Re: Ozzie st150 exhaust

Postby rositano » Thu Apr 07, 2016 3:26 am

No worries man. Appreciate the offer.

I just want to make the right choice of muffler, because it'll either 'make or break' the exhaust in terms of overall sound and drone.
It's the endless search for a freer flowing muffler without being too loud. I'm considering a lukey super turbo muffler (walker dynomax). These are your classic muscle car muffler which flows better than the older designs with the same internals. I've used one before on another car an it gave a nice euro sports car sound with a deep mellow tone and slight rasp. I'm aware that like the milltek, it's not a straight through in order to maintain some healthy levels of backpressure, which I hear is pretty important with the st150.
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